Multi-mode electromechanical variable transmission

ABSTRACT

A drive system includes a first gear set and a second gear set, each including a sun gear, a ring gear, a plurality of planetary gears coupling the sun gear to the ring gear, and a carrier rotationally supporting the plurality of planetary gears, a first electrical machine coupled to the sun gear of the first gear set, a second electrical machine coupled to the sun gear of the second gear set, a connecting shaft coupled to the ring gear of the first gear set, a driveshaft that transports power from the electrical machines to a tractive element, a first clutch selectively rotationally coupling the first carrier and the second carrier to the driveshaft, and at least one of a second clutch selectively rotationally coupling the second electrical machine to the connecting shaft and a third clutch selectively rotationally coupling the second gear set to the driveshaft.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/595,443, filed May 15, 2017, which is a continuation of U.S.application Ser. No. 14/624,285, filed Feb. 17, 2015, now U.S. Pat. No.9,651,120, both of which are incorporated herein by reference in theirentireties.

BACKGROUND

Internal combustion engine vehicles, hybrid vehicles, and electricvehicles, among other types of vehicles, include transmissions.Traditional vehicle transmissions use gears and gear trains to providespeed and torque conversions from a rotating power source (e.g., anengine, a motor, etc.) to another device (e.g., a drive shaft, wheels ofa vehicle, etc.). Transmissions include multiple gear ratios selectivelycoupled to the rotating power source with a mechanism that may alsoselectively couple an output to the various gear ratios.

SUMMARY

One exemplary embodiment relates to a drive system for a vehicle. Thedrive system includes a first gear set including a first sun gear, afirst ring gear, a first plurality of planetary gears coupling the firstsun gear to the first ring gear, and a first carrier rotationallysupporting the first plurality of planetary gears and a second gear setincluding a second sun gear, a second ring gear, a second plurality ofplanetary gears coupling the second sun gear to the second ring gear,and a second carrier rotationally supporting the second plurality ofplanetary gears. The first carrier is directly coupled to the secondcarrier. The drive system further includes a first electrical machinedirectly coupled to the first sun gear of the first gear set, a secondelectrical machine directly coupled to the second sun gear of the secondgear set, a connecting shaft coupled to the first ring gear of the firstgear set, a driveshaft configured to transport power from the firstelectrical machine and the second electrical machine to a tractiveelement of the vehicle, a first clutch selectively rotationally couplingthe first carrier and the second carrier to the driveshaft when engaged,and at least one of a second clutch selectively rotationally couplingthe second electrical machine to the connecting shaft when engaged and athird clutch selectively rotationally coupling the second gear set tothe driveshaft when engaged.

Another exemplary embodiment relates to a drive system for a vehicle.The drive system includes a first planetary gear set, a second planetarygear set directly coupled to the first planetary gear set, a connectingshaft coupled to the first planetary gear set, a first electromagneticdevice coupled to the first planetary gear set and including a firstshaft, a second electromagnetic device coupled to the second planetarygear set, selectively rotationally engaged with the connecting shaft,and including a second shaft, and an output selectively coupled to thefirst planetary gear set and the second planetary gear set. The firstplanetary gear set, the second planetary gear set, and the connectingshaft are radially aligned. The first shaft and the second shaft areradially aligned with the first planetary gear set, the second planetarygear set, and the connecting shaft. The connecting shaft extends throughthe second electromagnetic device and through the second planetary gearset to the first planetary gear set. The output is radially offset fromthe first planetary gear set, the second planetary gear set, and theconnecting shaft.

Another exemplary embodiment relates to a vehicle including a multi-modetransmission. The multi-mode transmission includes a first gear sethaving a first planetary gear carrier, a second gear set having a secondplanetary gear carrier, a first motor/generator coupled to the firstgear set, and a second motor/generator coupled to the second gear set.The first planetary gear carrier and the second planetary gear carrierare rotatably coupled. A connecting shaft is selectively coupled to thesecond gear set, and a drive axle is selectively coupled to themulti-mode transmission. During a first mode of the multi-modetransmission the connecting shaft is coupled to the secondmotor/generator and decoupled from the drive axle. During a second modeof the multi-mode transmission the connecting shaft is decoupled fromthe second motor/generator, the second motor/generator is selectivelycoupled to the drive axle, and the connecting shaft is coupled to thefirst motor/generator.

The invention is capable of other embodiments and of being carried outin various ways. Alternative exemplary embodiments relate to otherfeatures and combinations of features as may be recited herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIG. 1 is a schematic view of a drive train for a vehicle, according toan exemplary embodiment;

FIG. 2 is a detailed schematic view of the drive train of FIG. 1,according to an exemplary embodiment;

FIG. 3 is a schematic diagram of a control system for the drive train ofFIG. 1, according to an exemplary embodiment.

FIG. 4 is a detailed schematic view of a drive train configured in aneutral startup mode of operation, according to an exemplary embodiment;

FIG. 5 is a detailed schematic view of a drive train configured in apower generation mode of operation, according to an exemplaryembodiment;

FIG. 6 is a detailed schematic view of a drive train configured in a lowrange mode of operation, according to an exemplary embodiment;

FIG. 7 is a detailed schematic view of a drive train configured in a midrange mode of operation, according to an exemplary embodiment;

FIG. 8 is a detailed schematic view of a drive train configured in ahigh range mode of operation, according to an exemplary embodiment;

FIG. 9 is a detailed schematic view of a drive train configured in a lowspeed reverse mode of operation, according to an exemplary embodiment;and

FIG. 10 is a detailed schematic view of a drive train configured in ahigh speed reverse mode of operation, according to an exemplaryembodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentapplication is not limited to the details or methodology set forth inthe description or illustrated in the figures. It should also beunderstood that the terminology is for the purpose of description onlyand should not be regarded as limiting.

According to an exemplary embodiment, a multi-mode electromechanicalvariable transmission is provided as part of a vehicle and isselectively reconfigurable into one of a plurality of operating modes.The vehicle may also include an engine, a first electromagnetic device,and second electromagnetic device. In one embodiment, at least one ofthe first electromagnetic device and the second electromagnetic deviceprovides rotational mechanical energy to start the engine. In anotherembodiment, the engine provides a rotational mechanical energy input toboth the first and second electromagnetic devices such that eachoperates as a generator to generate electrical energy. In still otherembodiments, one of the first electromagnetic device and the secondelectromagnetic device are configured to receive a rotational mechanicalenergy output from at least one of the engine and the multi-modeelectromechanical variable transmission and provide an electrical energyoutput to power a control system and/or the other electromagneticdevice.

According to the exemplary embodiment shown in FIGS. 1-2, a vehicle 10includes an engine 20 coupled to a transmission, shown as transmission30. In one embodiment, engine 20 is configured to combust fuel andprovide a mechanical energy input to transmission 30. By way of example,engine 20 may be configured to provide a rotational mechanical energyinput to transmission 30. As shown in FIGS. 1-2, a first electricalmachine, electromagnetic device and/or motor/generator, shown as firstelectromagnetic device 40, and a second electrical machine,electromagnetic device and/or motor/generator, shown as secondelectromagnetic device 50, are coupled to transmission 30.

Referring again to the exemplary embodiment shown in FIG. 1, vehicle 10includes a front axle, shown as front axle 60, and a rear axle, shown asrear axle 70. As shown in FIG. 1, front axle 60 includes a pair oftractive elements, shown as tires 62, coupled to a front differential,shown as front differential 64. Rear axle 70 includes a pair of tractiveelements, shown as tires 72, coupled to a rear differential, shown asrear differential 74, according to an exemplary embodiment. According tothe exemplary embodiment shown in FIG. 1, front differential 64 iscoupled to transmission 30 with a front axle driveshaft 66 and reardifferential 74 is coupled to transmission 30 with a rear axledriveshaft 76. While shown as coupled to tires 62 and tires 72, frontdifferential 64 and rear differential 74 may be coupled to various othertypes of tractive elements (e.g., tracks, etc.), according toalternative embodiments. As shown in FIG. 1, front axle driveshaft 66and rear axle driveshaft 76 are configured to transport power from firstelectromagnetic device 40, second electromagnetic device 50, and engine20 to tires 62 and tires 72, respectively. Vehicle 10 may include aplurality of front differentials 64 that may be coupled or a pluralityof rear differentials 74 that may be coupled, according to variousalternative embodiments.

Engine 20 may be any source of rotational mechanical energy that isderived from a stored energy source. The stored energy source isdisposed onboard vehicle 10, according to an exemplary embodiment. Thestored energy source may include a liquid fuel or a gaseous fuel, amongother alternatives. In one embodiment, engine 20 includes an internalcombustion engine configured to be powered by at least one of gasoline,natural gas, and diesel fuel. According to various alternativeembodiments, engine 20 includes at least one of a turbine, a fuel cell,an electric motor or still another device. According to one exemplaryembodiment, engine 20 includes a twelve liter diesel engine capable ofproviding between approximately 400 horsepower and approximately 600horsepower and between approximately 400 foot pounds of torque andapproximately 2000 foot pounds of torque. In one embodiment, engine 20has a rotational speed (e.g., a rotational operational range, etc.) ofbetween 0 and 2,100 revolutions per minute. Engine 20 may be operated ata relatively constant speed (e.g., 1,600 revolutions per minute, etc.).In one embodiment, the relatively constant speed is selected based on anoperating condition of engine 20 (e.g., an operating speed relating to apoint of increased fuel efficiency, etc.).

In one embodiment, at least one of first electromagnetic device 40 andsecond electromagnetic device 50 provide a mechanical energy input totransmission 30. By way of example, at least one of firstelectromagnetic device 40 and second electromagnetic device 50 may beconfigured to provide a rotational mechanical energy input totransmission 30 (i.e., at least one of first electromagnetic device 40and second electromagnetic device 50 may operate as a motor, etc.). Atleast one of first electromagnetic device 40 and second electromagneticdevice 50 may receive a mechanical energy output from at least one ofengine 20 and transmission 30. By way of example, at least one of firstelectromagnetic device 40 and second electromagnetic device 50 may beconfigured to receive a rotational mechanical energy output from atleast one of engine 20 and transmission 30 and provide an electricalenergy output (i.e., at least one of first electromagnetic device 40 andsecond electromagnetic device 50 may operate as a generator, etc.).According to an exemplary embodiment, first electromagnetic device 40and second electromagnetic device 50 are capable of both providingmechanical energy and converting a mechanical energy input into anelectrical energy output (i.e., operate as a motor and a generator,etc.). The operational condition of first electromagnetic device 40 andsecond electromagnetic device 50 (e.g., as a motor, as a generator,etc.) may vary based on a mode of operation associated with transmission30.

According to the exemplary embodiment shown in FIG. 2, a drive systemfor a vehicle, shown as drive system 100, includes engine 20,transmission 30, first electromagnetic device 40, second electromagneticdevice 50, front axle driveshaft 66, and rear axle driveshaft 76. Asshown in FIG. 2, transmission 30 includes a first gear set, shown aspower split planetary 110, and a second gear set, shown as outputplanetary 120. In one embodiment, power split planetary 110 and outputplanetary 120 are disposed between first electromagnetic device 40 andsecond electromagnetic device 50. In an alternative embodiment, one orboth of power split planetary 110 and output planetary 120 arepositioned outside of (i.e., not between, etc.) first electromagneticdevice 40 and second electromagnetic device 50. As shown in FIG. 2,power split planetary 110 is directly coupled to engine 20.

Referring to the exemplary embodiment shown in FIG. 2, power splitplanetary 110 is a planetary gear set that includes a sun gear 112, aring gear 114, and a plurality of planetary gears 116. The plurality ofplanetary gears 116 couple sun gear 112 to ring gear 114, according toan exemplary embodiment. As shown in FIG. 2, a carrier 118 rotationallysupports the plurality of planetary gears 116. In one embodiment, firstelectromagnetic device 40 is directly coupled to sun gear 112 such thatpower split planetary 110 is coupled to first electromagnetic device 40.By way of example, first electromagnetic device 40 may include a shaft(e.g., a first shaft, an input shaft, an output shaft, etc.) directlycoupled to sun gear 112.

Referring still to the exemplary embodiment shown in FIG. 2, outputplanetary 120 is a planetary gear set that includes a sun gear 122, aring gear 124, and a plurality of planetary gears 126. The plurality ofplanetary gears 126 couple sun gear 122 to ring gear 124, according toan exemplary embodiment. As shown in FIG. 2, a carrier 128 rotationallysupports the plurality of planetary gears 126. In one embodiment, secondelectromagnetic device 50 is directly coupled to sun gear 122 such thatoutput planetary 120 is coupled to second electromagnetic device 50. Byway of example, second electromagnetic device 50 may include a shaft(e.g., a second shaft, an input shaft, an output shaft, etc.) directlycoupled to sun gear 122. Carrier 118 is directly coupled to carrier 128,thereby coupling power split planetary 110 to output planetary 120,according to the exemplary embodiment shown in FIG. 2. In oneembodiment, directly coupling carrier 118 to carrier 128 synchronizesrotational speeds of carrier 118 and carrier 128.

According to an exemplary embodiment, transmission 30 includes a firstclutch, shown as power split coupled clutch 130. In one embodiment,power split coupled clutch 130 is positioned downstream of power splitplanetary 110 (e.g., between power split planetary 110 and front axledriveshaft 66 or rear axle driveshaft 76, etc.). In an alternativeembodiment, power split coupled clutch 130 is directly coupled to engine20. As shown in FIG. 2, power split coupled clutch 130 is positioned toselectively couple power split planetary 110 and output planetary 120with a shaft, shown as output shaft 32. In one embodiment, power splitcoupled clutch 130 allows a vehicle to be towed without spinning thegears within transmission 30 (e.g., power split planetary 110, outputplanetary 120, etc.). Output shaft 32 may be coupled to rear axledriveshaft 76 and selectively coupled to front axle driveshaft with adeclutch assembly, shown as front declutch collar shift 34. Frontdeclutch collar shift 34 may be engaged and disengaged to selectivelycouple front axle driveshaft 66 to output shaft 32 of transmission 30(e.g., to facilitate operation of a vehicle in a rear-wheel-drive-onlymode, an all-wheel-drive mode, a four-wheel-drive mode, etc.).

As shown in FIG. 2, transmission 30 includes a second clutch, shown asinput coupled clutch 140. Input coupled clutch 140 is positioned toselectively couple second electromagnetic device 50 with engine 20,according to an exemplary embodiment. Input coupled clutch 140 maythereby selectively couple engine 20 to output planetary 120. As shownin FIG. 2, transmission 30 includes a shaft, shown as connecting shaft36. According to an exemplary embodiment, connecting shaft 36 extendsfrom engine 20, through second electromagnetic device 50, and throughoutput planetary 120 to power split planetary 110. Connecting shaft 36couples engine 20 with power split planetary 110, according to theexemplary embodiment shown in FIG. 2. In one embodiment, connectingshaft 36 directly couples engine 20 with ring gear 114 of power splitplanetary 110. Input coupled clutch 140 may selectively couple secondelectromagnetic device 50 with connecting shaft 36. According to anexemplary embodiment, the shaft (e.g., input/output shaft, etc.) offirst electromagnetic device 40 and the shaft (e.g., input/output shaft,etc.) of second electromagnetic device 50 are radially aligned withpower split planetary 110, output planetary 120, and connecting shaft 36(e.g., centerlines thereof are aligned, etc.). As shown in FIG. 2,transmission 30 includes a third clutch, shown as output coupled clutch150. Output coupled clutch 150 is positioned to selectively coupleoutput planetary 120 with output shaft 32, according to an exemplaryembodiment. In one embodiment, output shaft 32 is radially offset frompower split planetary 110, output planetary 120, and connecting shaft 36(e.g., radially offset from centerlines thereof, etc.).

Referring again to the exemplary embodiment shown in FIG. 2,transmission 30 includes a first brake, shown as power split brake 160.As shown in FIG. 2, power split brake 160 is positioned to selectivelyinhibit the movement of at least a portion of power split planetary 110(e.g., planetary gears 116, carrier 118, etc.) and output planetary 120(e.g., planetary gears 126, carrier 128, etc.). In other embodiments,transmission 30 does not include power split brake 160. Power splitbrake 160 may thereby be an optional component of transmission 30.According to an exemplary embodiment, transmission 30 includes a secondbrake (or a first brake in embodiments where transmission 30 does notinclude power split brake 160), shown as output brake 170. Output brake170 is positioned to selectively inhibit the movement of at least aportion of output planetary 120 (e.g., ring gear 124, etc.), accordingto an exemplary embodiment. In one embodiment, at least one of powersplit brake 160 and output brake 170 are biased into an engaged position(e.g., with a spring, etc.) and selectively disengaged (e.g., withapplication of pressurized hydraulic fluid, etc.). In other embodiments,power split brake 160 and output brake 170 are hydraulically-biased andspring released. In still other embodiments, the components oftransmission 30 are still otherwise engaged and disengaged (e.g.,pneumatically, etc.). By way of example, output brake 170 and outputcoupled clutch 150 may be engaged simultaneously to function as adriveline brake (e.g., a braking mechanism to slow down a vehicle,etc.). By way of another example, power split brake 160 and power splitcoupled clutch 130 may be engaged simultaneously to function as adriveline brake.

As shown in FIG. 2, transmission 30 includes a gear set 180 that couplescarrier 118 and carrier 128 to output shaft 32. In one embodiment, gearset 180 includes a first gear, shown as gear 182, in meshing engagementwith a second gear, shown as gear 184. As shown in FIG. 2, gear 182 isrotatably coupled to carrier 118 and carrier 128. By way of example,gear 182 may be fixed to a component (e.g., shaft, tube, etc.) thatcouples carrier 118 and carrier 128. As shown in FIG. 2, power splitcoupled clutch 130 is positioned to selectively couple gear 184 withoutput shaft 32 when engaged. With power split coupled clutch 130disengaged, relative movement (e.g., rotation, etc.) may occur betweengear 184 and output shaft 32. Power split brake 160 may be positioned toselectively limit the movement of gear 184 when engaged to thereby limitthe movement of gear 182, carrier 118, and carrier 128.

According to an exemplary embodiment, transmission 30 includes a gearset, shown as gear set 190, that couples output planetary 120 to outputshaft 32. As shown in FIG. 2, gear set 190 includes a first gear, shownas gear 192, coupled to ring gear 124 of output planetary 120. Gear 192is in meshing engagement with a second gear, shown as gear 194,according to an exemplary embodiment. As shown in FIG. 2, gear 194 iscoupled to a third gear, shown as gear 196. In other embodiments, gear192 is directly coupled with gear 196. By way of example, gear set 190may not include gear 194, and gear 192 may be directly coupled to (e.g.,in meshing engagement with, etc.) gear 196. As shown in FIG. 2, outputcoupled clutch 150 is positioned to selectively couple gear 196 withoutput shaft 32 when engaged. With output coupled clutch 150 disengaged,relative movement (e.g., rotation, etc.) may occur between gear 196 andoutput shaft 32. By way of example, output coupled clutch 150 may beengaged to couple ring gear 124 to output shaft 32. Output brake 170 ispositioned to selectively limit the movement of gear 192 when engaged tothereby also limit the movement of ring gear 124, gear 194, and gear196.

According to the exemplary embodiment shown in FIG. 3, a control system200 for a vehicle includes a controller 210. In one embodiment,controller 210 is configured to selectively engage, selectivelydisengage, or otherwise communicate with components of the vehicleaccording to various modes of operation. As shown in FIG. 3, controller210 is coupled to engine 20. In one embodiment, controller 210 isconfigured to selectively engage engine 20 (e.g., interface with athrottle of, etc.) such that an output of engine 20 spins at a targetrate. Controller 210 is coupled to first electromagnetic device 40 andsecond electromagnetic device 50, according to an exemplary embodiment,and may send and receive signals therewith. By way of example,controller 210 may send command signals relating to at least one of atarget rotational speed and a target rotation direction for firstelectromagnetic device 40 and second electromagnetic device 50. As shownin FIG. 3, first electromagnetic device 40 and second electromagneticdevice 50 are electrically coupled. By way of example, power generatedby first electromagnetic device 40 may be utilized by secondelectromagnetic device 50 (e.g., to provide an output torque as a motor,etc.), or power generated by second electromagnetic device 50 may beutilized by first electromagnetic device 40 (e.g., to provide an outputtorque as a motor, etc.).

According to the exemplary embodiment shown in FIG. 3, control system200 includes a user interface 220 that is coupled to controller 210. Inone embodiment, user interface 220 includes a display and an operatorinput. The display may be configured to display a graphical userinterface, an image, an icon, or still other information. In oneembodiment, the display includes a graphical user interface configuredto provide general information about the vehicle (e.g., vehicle speed,fuel level, warning lights, etc.). The graphical user interface may alsobe configured to display a current mode of operation, various potentialmodes of operation, or still other information relating to transmission30 or drive system 100. By way of example, the graphical user interfacemay be configured to provide specific information regarding theoperation of drive system 100 (e.g., whether power split coupled clutch130, input coupled clutch 140, output coupled clutch 150, power splitbrake 160, and output brake 170 are engaged or disengaged, a faultcondition where at least one of power split coupled clutch 130, inputcoupled clutch 140, output coupled clutch 150, power split brake 160,and output brake 170 fail to engage or disengage in response to acommand signal, etc.).

The operator input may be used by an operator to provide commands to atleast one of engine 20, transmission 30, first electromagnetic device40, second electromagnetic device 50, and drive system 100 or stillanother component of the vehicle. The operator input may include one ormore buttons, knobs, touchscreens, switches, levers, or handles. In oneembodiment, an operator may press a button to change the mode ofoperation for at least one of transmission 30, and drive system 100, andthe vehicle. The operator may be able to manually control some or allaspects of the operation of transmission 30 using the display and theoperator input. In should be understood that any type of display orinput controls may be implemented with the systems and methods describedherein.

Controller 210 may be implemented as a general-purpose processor, anapplication specific integrated circuit (ASIC), one or more fieldprogrammable gate arrays (FPGAs), a digital-signal-processor (DSP),circuits containing one or more processing components, circuitry forsupporting a microprocessor, a group of processing components, or othersuitable electronic processing components. According to the exemplaryembodiment shown in FIG. 3, controller 210 includes a processing circuit212 and a memory 214. Processing circuit 212 may include an ASIC, one ormore FPGAs, a DSP, circuits containing one or more processingcomponents, circuitry for supporting a microprocessor, a group ofprocessing components, or other suitable electronic processingcomponents. In some embodiments, processing circuit 212 is configured toexecute computer code stored in memory 214 to facilitate the activitiesdescribed herein. Memory 214 may be any volatile or non-volatilecomputer-readable storage medium capable of storing data or computercode relating to the activities described herein. According to anexemplary embodiment, memory 214 includes computer code modules (e.g.,executable code, object code, source code, script code, machine code,etc.) configured for execution by processing circuit 212. Memory 214includes various actuation profiles corresponding to modes of operation(e.g., for transmission 30, for drive system 100, for a vehicle, etc.),according to an exemplary embodiment. In some embodiments, controller210 may represent a collection of processing devices (e.g., servers,data centers, etc.). In such cases, processing circuit 212 representsthe collective processors of the devices, and memory 214 represents thecollective storage devices of the devices.

Referring next to the exemplary embodiments shown in FIGS. 4-10,transmission 30 is configured to operate according to a plurality ofmodes of operation. Various modes of operation for transmission 30 areidentified below in Table 1. In other embodiments, a vehicle havingtransmission 30 is configured to operate according to the various modesof operation shown in FIGS. 4-10 and identified below in Table 1.

TABLE 1 Power Power Split Output Input Split Coupled Coupled OutputCoupled Mode of Brake Clutch Clutch Brake Clutch Operation 160 130 150170 140 High Speed X X Reverse Low Speed X X Reverse Power X XGeneration Neutral/ Vehicle Start Low Range X X Mid Range X X High RangeX X

As shown in Table 1, an “X” represents a component of drive system 100(e.g., power split brake 160, power split coupled clutch 130, etc.) thatis engaged or closed during the respective modes of operation. In otherembodiments, power split brake 160 may be engaged during a neutralstartup mode.

As shown in FIG. 4, transmission 30 is selectively reconfigured into aneutral startup mode. In one embodiment, rotation of firstelectromagnetic device 40 rotates connecting shaft 36 to start engine20. An energy storage device (e.g., a capacitor, a battery, etc.)configured to store energy (e.g., electrical energy, chemical energy,etc.) may be associated with drive system 100. By way of example, firstelectromagnetic device 40 may be configured to use the stored energy tostart engine 20 by providing a rotational mechanical energy input (e.g.,a torque, etc.) to engine 20 via connecting shaft 36. In an alternativeembodiment, engine 20 includes a traditional starting mechanism (e.g., astarter motor, etc.) configured to start engine 20. Engine 20 mayprovide a rotational mechanical energy input to at least one of firstelectromagnetic device 40 and/or second electromagnetic device 50. Thefirst electromagnetic device 40 and second electromagnetic device 50 maybe brought up to a threshold (e.g., a threshold speed, a threshold speedfor a target period of time, a threshold power generation, a thresholdpower generation for a target period of time, etc.) that establishes arequisite DC bus voltage. Both first electromagnetic device 40 andsecond electromagnetic device 50 may thereafter be activated andcontrolled within and/or to desired states. The power electronics ofcontrol system 200 that control the motor-to-motor functions may bebrought online during the neutral startup mode.

In one embodiment, transmission 30 includes power split brake 160, andpower split brake 160 is engaged when transmission 30 is configured inthe neutral startup mode. According to an exemplary embodiment, engagingpower split brake 160 selectively limits the rotational movement ofportions of both power split planetary 110 and output planetary 120. Byway of example, engaging power split brake 160 may inhibit therotational movement of gear 182, gear 184, and carrier 118 such thateach remains rotationally fixed. Accordingly, carrier 128 also remainsrotationally fixed because carrier 118 and carrier 128 are directlycoupled. According to an exemplary embodiment, an energy flow path inthe neutral startup mode includes: first electromagnetic device 40providing a rotational mechanical energy input to sun gear 112 that isreceived by the plurality of planetary gears 116; the plurality ofplanetary gears 116 rotating about central axes thereof (e.g., planetarygears 116 may or may not rotate about sun gear 112 because carrier 118may or may not be rotationally fixed, etc.); the plurality of planetarygears 116 conveying the rotational mechanical energy to ring gear 114;ring gear 114 transferring the rotational mechanical energy toconnecting shaft 36 such that the rotational mechanical energy providedby first electromagnetic device 40 starts engine 20. Another energy flowpath in the neutral startup mode may include engine 20 providing arotational mechanical energy input to ring gear 114 that is received bythe plurality of planetary gears 116; the plurality of planetary gears116 rotating about central axes thereof (e.g., planetary gears 116 mayor may not rotate about sun gear 112 because carrier 118 may or may notbe rotationally fixed, etc.); the plurality of planetary gears 116conveying the rotational mechanical energy to sun gear 112; and sun gear112 conveying the rotational mechanical energy to first electromagneticdevice 40 to bring first electromagnetic device 40 up to the thresholdfor establishing a requisite DC bus voltage and controlling firstelectromagnetic device 40 and/or second electromagnetic device 50 in adesired state.

Power split brake 160 may be used to isolate engine 20, firstelectromagnetic device 40, and second electromagnetic device 50 fromoutput shaft 32 in the neutral startup mode. Such isolation maysubstantially eliminate a forward lurch potential of the vehicle (e.g.,transmission 30 does not provide an output torque to tires 62 and/ortires 72, etc.). By way of example, the neutral startup mode utilizingpower split brake 160 may be used to start engine 20, establish arequisite DC bus voltage, or otherwise export power without relying oncontroller 210 to engage first electromagnetic device 40 and/or secondelectromagnetic device 50.

As shown in FIG. 5, transmission 30 is selectively reconfigured into apower generation mode such that rotation of connecting shaft 36 rotatesfirst electromagnetic device 40 and second electromagnetic device 50 togenerate electrical power. In one embodiment, the electrical power isstored for future use. In another embodiment, the electrical power isused to power internal devices (e.g., control system 200, components ofthe vehicle, etc.) and/or external devices. As shown in FIG. 5 and Table1, power split brake 160 and input coupled clutch 140 are engaged whentransmission 30 is configured in the power generation mode. As shown inFIG. 5, both power split coupled clutch 130 and output coupled clutch150 are not engaged such that engine 20 is isolated from output shaft32. Engine 20 does not provide rotational mechanical energy to tires 62or tires 72 during the power generation mode.

According to an exemplary embodiment, engine 20 provides a rotationalmechanical energy input to connecting shaft 36, which drives both firstelectromagnetic device 40 and second electromagnetic device 50. As shownin FIG. 5, second electromagnetic device 50 is rotationally coupled toengine 20 via the engagement of input coupled clutch 140 with connectingshaft 36 such that second electromagnetic device 50 generates electricalpower. The rotational mechanical energy of connecting shaft 36 is alsoprovided to ring gear 114 of power split planetary 110. Engaging powersplit brake 160 inhibits the rotational movement of gear 182, gear 184,and carrier 118. Ring gear 114 conveys the rotational mechanical energyfrom connecting shaft 36 to the plurality of planetary gears 116. Theplurality of planetary gears 116 rotate about central axes thereof,while remaining rotationally fixed relative to sun gear 112 such thatthe rotational mechanical energy is transferred to sun gear 112. Sungear 112 provides the rotational mechanical energy from engine 20 tofirst electromagnetic device 40 via the shaft of first electromagneticdevice 40 such that first electromagnetic device 40 generates electricalpower.

As shown in FIG. 6, transmission 30 is selectively reconfigured into alow range mode of operation such that transmission 30 allows for a lowoutput speed operation with a high output torque. The low range modeincreases a vehicle's gradability (e.g., facilitates the vehiclemaintaining speed on a grade, etc.). In one embodiment, engine 20provides a rotational mechanical energy input to transmission 30 suchthat first electromagnetic device 40 generates electrical power andsecond electromagnetic device 50 uses the generated electrical power toprovide a rotational mechanical energy input to transmission 30. Assuch, engine 20 and second electromagnetic device 50 provide arotational mechanical energy input to drive at least one of tires 62 andtires 72. In an alternative embodiment, first electromagnetic device 40operates as a motor and second electromagnetic device 50 operates as agenerator when transmission 30 is configured in the low range mode.

As shown in FIG. 6 and Table 1, power split coupled clutch 130 andoutput coupled clutch 150 are engaged when transmission 30 is configuredin the low range mode. As shown in FIG. 6, power split coupled clutch130 and output coupled clutch 150 couple gear set 180 and gear set 190to output shaft 32, respectively. Accordingly, when engine 20 provides arotational mechanical energy input to transmission 30, both power splitplanetary 110 and output planetary 120 drive output shaft 32 via gearset 180 and gear set 190, respectively. According to the exemplaryembodiment shown in FIG. 6, an energy flow path for the low rangeincludes: engine 20 providing a rotational mechanical energy input toconnecting shaft 36; connecting shaft 36 conveying the rotationalmechanical energy to ring gear 114; ring gear 114 causing the pluralityof planetary gears 116 to rotate about central axes thereof, as well asabout sun gear 112 such that both carrier 118 and sun gear 112 rotate;and the rotation of sun gear 112 driving first electromagnetic device 40such that it operates as a generator (e.g., generates electrical energy,etc.).

Referring still to FIG. 6, the rotation of carrier 118 drives bothcarrier 128 and gear set 180. Carrier 128 drives the plurality ofplanetary gears 126 to rotate about sun gear 122 and about central axesthereof. In one embodiment, second electromagnetic device 50 receiveselectrical energy generated by first electromagnetic device 40.Accordingly, second electromagnetic device 50 operates as a motor,providing a rotational mechanical energy input to sun gear 122. The sungear 122 conveys the rotational mechanical energy to the plurality ofplanetary gears 126 such that each further rotates about the centralaxis thereof. The plurality of planetary gears 126 drive ring gear 124,and the rotation of ring gear 124 drives gear set 190. According to theexemplary embodiment shown in FIG. 6, gear set 180 and gear set 190transfer a torque to and from output shaft 32 with power split coupledclutch 130 and output coupled clutch 150 engaged. As such, engine 20 andsecond electromagnetic device 50 move a vehicle at a low speed with ahigh output torque.

As shown in FIG. 7, transmission 30 is selectively reconfigured into amid range mode of operation such that transmission 30 allows for a midrange output speed operation. The mid range mode may improve low outputspeed torque and high output speed power. In one embodiment, engine 20provides a rotational mechanical energy input such that firstelectromagnetic device 40 generates electrical power, and secondelectromagnetic device 50 uses the generated electrical power to providea rotational mechanical energy input to transmission 30. As such, secondelectromagnetic device 50 provides a rotational mechanical energy inputto drive at least one of tires 62 and tires 72. In an alternativeembodiment, second electromagnetic device 50 operates as a generator andfirst electromagnetic device 40 operates as a motor when transmission 30is configured in the mid range mode. In still another alternativeembodiment, both first electromagnetic device 40 and secondelectromagnetic device 50 operate as a generator in the mid range mode.

As shown in FIG. 7 and Table 1, power split coupled clutch 130 andoutput brake 170 are engaged when transmission 30 is configured in themid range mode. As shown in FIG. 7, output brake 170 inhibits therotation of gear set 190 (e.g., gear 192, gear 194, gear 196, etc.).Output brake 170 thereby rotationally fixes ring gear 124. In oneembodiment, engaging output brake 170 substantially eliminates a powerdip between output and input modes of transmission 30. According to theexemplary embodiment shown in FIG. 7, an energy flow path for the midrange mode includes: engine 20 providing a rotational mechanical energyinput to connecting shaft 36 that is conveyed to ring gear 114; and ringgear 114 driving the plurality of planetary gears 116 to rotate aboutcentral axes thereof, as well as about sun gear 112 such that bothcarrier 118 and sun gear 112 rotate.

Referring still to FIG. 7, the rotation of carrier 118 drives carrier128, which rotates the plurality planetary gears 126 about central axesthereof, as well as about sun gear 122. With ring gear 124 fixed byoutput brake 170, second electromagnetic device 50 may operate as amotor. In one embodiment, second electromagnetic device 50 receiveselectrical energy generated by first electromagnetic device 40.Accordingly, first electromagnetic device 40 operates as a generator,removing a rotational mechanical energy from sun gear 112. The sun gear122 conveys the rotational mechanical torque to the plurality ofplanetary gears 126 such that each further rotates about sun gear 122(e.g., at an increased rotational speed, etc.). The rotation of theplurality of planetary gears 126 (e.g., effected by sun gear 122, etc.)drives carrier 128 and thereby gear set 180. As shown in FIG. 7, powersplit coupled clutch 130 couples gear set 180 to output shaft 32 suchthat the rotational mechanical energy of gear set 180, received fromsecond electromagnetic device 50, drives output shaft 32 at a mid rangeoutput speed and may thereby drive a vehicle at a mid range outputspeed.

As shown in FIG. 8, transmission 30 is selectively reconfigured into ahigh range mode of operation such that transmission 30 allows for a highoutput speed operation. In one embodiment, engine 20 provides arotational mechanical energy input such that second electromagneticdevice 50 generates electrical power and first electromagnetic device 40uses the generated electrical power to provide a rotational mechanicalenergy input to transmission 30. As such, engine 20 and firstelectromagnetic device 40 provide a rotational mechanical energy inputto drive at least one of tires 62 and tires 72. In an alternativeembodiment, first electromagnetic device 40 operates as a generator andsecond electromagnetic device 50 operates as a motor when transmission30 is configured in the medium range mode.

As shown in FIG. 8 and Table 1, power split coupled clutch 130 and inputcoupled clutch 140 are engaged when transmission 30 is configured in thehigh range mode. As shown in FIG. 8, the engagement of input coupledclutch 140 with connecting shaft 36 rotationally couples engine 20 andsecond electromagnetic device 50. By way of example, engine 20 mayprovide a rotational mechanical energy input to connecting shaft 36 suchthat second electromagnetic device 50 generates electrical energy. Inone embodiment, first electromagnetic device 40 receives the electricalenergy generated by second electromagnetic device 50. Accordingly, firstelectromagnetic device 40 operates as a motor, providing a rotationalmechanical energy input to sun gear 112 that drives the plurality ofplanetary gears 116.

Referring still to FIG. 8, the power from engine 20 is transferred toring gear 114 and the plurality of planetary gears 116. The plurality ofplanetary gears 116 are driven by both engine 20 (e.g., via ring gear114, etc.) and first electromagnetic device 40 (e.g., via sun gear 112,etc.). Carrier 118 rotates, which drives gear set 180. As shown in FIG.8, power split coupled clutch 130 couples gear set 180 to output shaft32 such that the rotational mechanical energy provided by engine 20 andfirst electromagnetic device 40 drives a vehicle at a high range speed.

As shown in FIG. 9, transmission 30 is selectively reconfigured into alow speed reverse mode of operation. In one embodiment, engine 20provides a rotational mechanical energy input to transmission 30 suchthat first electromagnetic device 40 generates electrical power andsecond electromagnetic device 50 uses the generated electrical power toprovide a rotational mechanical energy input to transmission 30. Assuch, engine 20 and second electromagnetic device 50 provide arotational mechanical energy input to drive at least one of tires 62 andtires 72 in a reverse direction (e.g., backwards, etc.). In analternative embodiment, first electromagnetic device 40 operates as amotor and second electromagnetic device 50 operates as a generator whentransmission 30 is configured in the low speed reverse mode.

As shown in FIG. 9 and Table 1, power split coupled clutch 130 andoutput coupled clutch 150 are engaged when transmission 30 is configuredin the low speed reverse mode. As shown in FIG. 9, the low speed reversemode is substantially similar to the low range mode of FIG. 6 in thatpower split coupled clutch 130 and output coupled clutch 150 couple bothgear set 180 and gear set 190 to output shaft 32. In the low speedreverse mode, second electromagnetic device 50 may provide a rotationalmechanical energy input to transmission 30 in an opposite direction ascompared to the low range mode of FIG. 6.

As shown in FIG. 10, transmission 30 is selectively reconfigured into ahigh speed reverse mode of operation such that transmission 30 allowsfor a high reverse output speed operation. In one embodiment, engine 20provides a rotational mechanical energy input such that firstelectromagnetic device 40 generates electrical power, and secondelectromagnetic device 50 uses the generated electrical power to providea rotational mechanical energy input to transmission 30. As such, secondelectromagnetic device 50 provides a rotational mechanical energy inputto drive at least one of tires 62 and tires 72. In an alternativeembodiment, second electromagnetic device 50 operates as a generator andfirst electromagnetic device 40 operates as a motor when transmission 30is configured in the high speed reverse mode. In still anotheralternative embodiment, both first electromagnetic device 40 and secondelectromagnetic device 50 operate as a generator in the high speedreverse mode.

As shown in FIG. 10 and Table 1, power split coupled clutch 130 andoutput brake 170 are engaged when transmission 30 is configured in thehigh speed reverse mode. As shown in FIG. 10, output brake 170 inhibitsthe rotation of gear set 190 (e.g., gear 192, gear 194, gear 196, etc.).Output brake 170 thereby rotationally fixes ring gear 124. According tothe exemplary embodiment shown in FIG. 10, an energy flow path for thehigh speed reverse mode includes: engine 20 providing a rotationalmechanical energy input to connecting shaft 36 that is conveyed to ringgear 114; and ring gear 114 driving the plurality of planetary gears 116to rotate about central axes thereof, as well as about sun gear 112 suchthat both carrier 118 and sun gear 112 rotate.

Referring still to FIG. 10, the rotation of carrier 118 drives carrier128, which rotates the plurality planetary gears 126 about central axesthereof, as well as about sun gear 122. With ring gear 124 fixed byoutput brake 170, second electromagnetic device 50 may operate as amotor. In one embodiment, second electromagnetic device 50 receiveselectrical energy generated by first electromagnetic device 40.Accordingly, first electromagnetic device 40 operates as a generator,removing a rotational mechanical energy from sun gear 112. The sun gear122 conveys the rotational mechanical torque to the plurality ofplanetary gears 126 such that each further rotates about sun gear 122(e.g., at an increased rotational speed, etc.). The rotation of theplurality of planetary gears 126 (e.g., effected by sun gear 122, etc.)drives carrier 128 and thereby gear set 180. As shown in FIG. 10, powersplit coupled clutch 130 couples gear set 180 to output shaft 32 suchthat the rotational mechanical energy of gear set 180, received fromsecond electromagnetic device 50, drives output shaft 32 at a highreverse output speed and may thereby drive a vehicle at a high reverseoutput speed.

According to an alternative embodiment, transmission 30 is selectivelyreconfigured into a high speed reverse mode of operation (e.g., a serieselectric mode, etc.) whereby output coupled clutch 150 and the optionalpower split brake 160 are engaged. In such a high speed reverse mode,engine 20 may be coupled to first electromagnetic device 40 such thatrotation of first electromagnetic device 40 by engine 20 generateselectric power to operate second electromagnetic device 50 as a motor.According to an exemplary embodiment, power split brake 160 increasesthe reverse range (e.g., potential speed range while in reverse, etc.)without increasing the gear speeds of transmission 30 to substantiallevels. Output coupled clutch 150 may couple output planetary 120 andgear set 190 to output shaft 32 such that second electromagnetic device50 provides a mechanical output to output shaft 32.

Power split brake 160 may inhibit the rotational movement of gear 182,gear 184, and carrier 118 such that each remains rotationally fixed.Accordingly, carrier 128 remains rotationally fixed. Engine 20 mayprovide a rotational mechanical energy input to connecting shaft 36.Connecting shaft 36 conveys the rotational mechanical energy to ringgear 114, which drives the plurality of planetary gears 116 to rotateabout central axes thereof, in turn rotating sun gear 112. Firstelectromagnetic device 40 receives the rotational mechanical energy fromengine 20 to generate electrical power. In one embodiment, theelectrical power is used by second electromagnetic device 50 to drivesun gear 122. Sun gear 122 causes the plurality of planetary gears 126to rotate about central axes thereof to drive ring gear 124. Ring gear124 drives gear set 190 such that the rotational mechanical energyprovided by second electromagnetic device 50 drives output shaft 32 andthereby a vehicle at a high speed in a reverse direction.

According to an alternative embodiment, engine 20 does not provide arotational mechanical energy input to drive a vehicle. By way ofexample, first electromagnetic device 40, second electromagnetic device50, and/or another device may store energy during the above mentionedmodes of operation. When sufficient energy is stored (e.g., above athreshold level, etc.), at least one of first electromagnetic device 40and second electromagnetic device 50 may provide a rotational mechanicalenergy input to transmission 30 such that the vehicle is driven withoutan input from engine 20 (e.g., an electric mode, etc.).

Although the figures may show a specific order of method steps, theorder of the steps may differ from what is depicted. Also two or moresteps may be performed concurrently or with partial concurrence. Suchvariation will depend on the software and hardware systems chosen and ondesigner choice. All such variations are within the scope of thedisclosure. Likewise, software implementations could be accomplishedwith standard programming techniques with rule-based logic and otherlogic to accomplish the various connection steps, processing steps,comparison steps, and decision steps. contrariwise

As utilized herein, the terms “approximately”, “about”, “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” “connected,” and the like, as used herein, mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent, etc.) or moveable (e.g.,removable, releasable, etc.). Such joining may be achieved with the twomembers or the two members and any additional intermediate members beingintegrally formed as a single unitary body with one another or with thetwo members or the two members and any additional intermediate membersbeing attached to one another.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below,” “between,” etc.) are merely used to describe theorientation of various elements in the figures. It should be noted thatthe orientation of various elements may differ according to otherexemplary embodiments, and that such variations are intended to beencompassed by the present disclosure.

It is important to note that the construction and arrangement of theelectromechanical variable transmission as shown in the exemplaryembodiments is illustrative only. Although only a few embodiments of thepresent disclosure have been described in detail, those skilled in theart who review this disclosure will readily appreciate that manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multiple partsor elements. It should be noted that the elements and/or assemblies ofthe components described herein may be constructed from any of a widevariety of materials that provide sufficient strength or durability, inany of a wide variety of colors, textures, and combinations.Accordingly, all such modifications are intended to be included withinthe scope of the present inventions. Other substitutions, modifications,changes, and omissions may be made in the design, operating conditions,and arrangement of the preferred and other exemplary embodiments withoutdeparting from scope of the present disclosure or from the spirit of theappended claims.

What is claimed is:
 1. A drive system for a vehicle, comprising: a firstgear set including a first sun gear, a first ring gear, a firstplurality of planetary gears coupling the first sun gear to the firstring gear, and a first carrier rotationally supporting the firstplurality of planetary gears; a second gear set including a second sungear, a second ring gear, a second plurality of planetary gears couplingthe second sun gear to the second ring gear, and a second carrierrotationally supporting the second plurality of planetary gears, whereinthe first carrier is directly coupled to the second carrier; a firstelectrical machine directly coupled to the first sun gear of the firstgear set; a second electrical machine directly coupled to the second sungear of the second gear set; a connecting shaft coupled to the firstring gear of the first gear set; a driveshaft configured to transportpower from the first electrical machine and the second electricalmachine to a tractive element of the vehicle; a first clutch selectivelyrotationally coupling the first carrier and the second carrier to thedriveshaft when engaged; a second clutch selectively rotationallycoupling the second electrical machine to the connecting shaft whenengaged; and a third clutch selectively rotationally coupling the secondgear set to the driveshaft when engaged.
 2. The drive system of claim 1,wherein the drive system is selectively reconfigurable into a first modewhereby the first clutch and the third clutch are engaged, and whereinthe drive system is selectively reconfigurable into a second modewhereby the first clutch and the second clutch are engaged.
 3. The drivesystem of claim 1, further comprising a brake positioned to selectivelylimit a rotational movement of the second ring gear, wherein the drivesystem is selectively reconfigurable into a mode whereby the firstclutch and the brake are engaged.
 4. The drive system of claim 1,further comprising a brake positioned to selectively limit a rotation ofthe first carrier and the second carrier, wherein the drive system isselectively reconfigurable into a mode whereby the brake and the secondclutch are engaged.
 5. The drive system of claim 4, wherein the drivesystem is selectively reconfigurable into a second mode whereby thebrake and the third clutch are engaged.
 6. The drive system of claim 5,further comprising a second brake positioned to selectively limit arotational movement of the second ring gear.
 7. A drive system for avehicle, comprising: a first planetary gear set; a second planetary gearset directly coupled to the first planetary gear set; a connecting shaftcoupled to the first planetary gear set, wherein the first planetarygear set, the second planetary gear set, and the connecting shaft areradially aligned; a first electromagnetic device coupled to the firstplanetary gear set, wherein the first electromagnetic device includes afirst shaft; a second electromagnetic device coupled to the secondplanetary gear set and selectively rotationally engaged with theconnecting shaft, wherein the second electromagnetic device includes asecond shaft, wherein the first shaft and the second shaft are radiallyaligned with the first planetary gear set, the second planetary gearset, and the connecting shaft, and wherein the connecting shaft extendsthrough the second electromagnetic device and through the secondplanetary gear set to the first planetary gear set; and an outputselectively coupled to the first planetary gear set and the secondplanetary gear set, wherein the output is radially offset from the firstplanetary gear set, the second planetary gear set, and the connectingshaft.
 8. The drive system of claim 7, further comprising a brakepositioned to selectively limit a rotational movement of the secondplanetary gear set.
 9. The drive system of claim 7, wherein the drivesystem is selectively reconfigurable into a first mode whereby theoutput is coupled to the first planetary gear set and the secondplanetary gear set, wherein the drive system is selectivelyreconfigurable into a second mode whereby the output is coupled to thefirst planetary gear set and a rotational movement of the secondplanetary gear set is limited, and wherein the drive system isselectively reconfigurable into a third mode whereby the output iscoupled to the first planetary gear set and the second electromagneticdevice is rotationally engaged with the connecting shaft.
 10. The drivesystem of claim 7, wherein the first planetary gear set and the secondplanetary gear set are disposed between the first electromagnetic deviceand the second electromagnetic device.
 11. The drive system of claim 7,further comprising a brake positioned to selectively limit a rotationalmovement of the first planetary gear set when engaged.
 12. The drivesystem of claim 11, wherein the drive system is selectivelyreconfigurable into a mode whereby the brake is engaged and the secondelectromagnetic device is rotationally engaged with the connectingshaft.
 13. The drive system of claim 7, wherein the drive system isselectively reconfigurable into a mode whereby the output is coupled tothe first planetary gear set and the second electromagnetic device isrotationally engaged with the connecting shaft.
 14. A vehicle,comprising: a multi-mode transmission including: a first gear set havinga first planetary gear carrier and a second gear set having a secondplanetary gear carrier, wherein the first planetary gear carrier and thesecond planetary gear carrier are rotatably coupled; a firstmotor/generator coupled to the first gear set; and a secondmotor/generator coupled to the second gear set; a connecting shaftselectively coupled to the second gear set; and a drive axle selectivelycoupled to the multi-mode transmission; wherein during a first mode ofthe multi-mode transmission the connecting shaft is coupled to thesecond motor/generator and decoupled from the drive axle, and whereinduring a second mode of the multi-mode transmission the connecting shaftis decoupled from the second motor/generator, the second motor/generatoris selectively coupled to the drive axle, and the connecting shaft iscoupled to the first motor/generator.
 15. The vehicle of claim 14,further comprising a first clutch positioned to selectively couple thefirst planetary gear carrier and the second planetary gear carrier tothe drive axle.
 16. The vehicle of claim 15, further comprising a brakepositioned to selectively limit movement of the first planetary gearcarrier and the second planetary gear carrier when engaged.
 17. Thevehicle of claim 16, further comprising a second brake positioned toselectively limit movement of a ring gear of the second gear set. 18.The vehicle of claim 17, further comprising a second clutch positionedto selectively couple the second motor/generator to the connectingshaft, wherein during a third mode of the multi-mode transmission thefirst clutch and the second brake are engaged, and wherein during afourth mode of operation the first clutch and the second clutch areengaged.
 19. The vehicle of claim 18, further comprising a third clutchpositioned to selectively couple the second gear set to the drive axle,wherein during a fifth mode of the multi-mode transmission the firstclutch and the third clutch are engaged.
 20. A drive system for avehicle, comprising: a first gear set including a first sun gear, afirst ring gear, a first plurality of planetary gears coupling the firstsun gear to the first ring gear, and a first carrier rotationallysupporting the first plurality of planetary gears; a second gear setincluding a second sun gear, a second ring gear, a second plurality ofplanetary gears coupling the second sun gear to the second ring gear,and a second carrier rotationally supporting the second plurality ofplanetary gears, wherein the first carrier is directly coupled to thesecond carrier; a first electrical machine directly coupled to the firstsun gear of the first gear set; a second electrical machine directlycoupled to the second sun gear of the second gear set; a connectingshaft coupled to the first ring gear of the first gear set; a driveshaftconfigured to transport power from the first electrical machine and thesecond electrical machine to a tractive element of the vehicle; a firstclutch selectively rotationally coupling the first carrier and thesecond carrier to the driveshaft when engaged; at least one of: a secondclutch selectively rotationally coupling the second electrical machineto the connecting shaft when engaged; and a third clutch selectivelyrotationally coupling the second gear set to the driveshaft whenengaged; and a brake positioned to selectively limit a rotationalmovement of the second ring gear, wherein the drive system isselectively reconfigurable into a mode whereby the first clutch and thebrake are engaged.
 21. A drive system for a vehicle, comprising: a firstgear set including a first sun gear, a first ring gear, a firstplurality of planetary gears coupling the first sun gear to the firstring gear, and a first carrier rotationally supporting the firstplurality of planetary gears; a second gear set including a second sungear, a second ring gear, a second plurality of planetary gears couplingthe second sun gear to the second ring gear, and a second carrierrotationally supporting the second plurality of planetary gears, whereinthe first carrier is directly coupled to the second carrier; a firstelectrical machine directly coupled to the first sun gear of the firstgear set; a second electrical machine directly coupled to the second sungear of the second gear set; a connecting shaft coupled to the firstring gear of the first gear set; a driveshaft configured to transportpower from the first electrical machine and the second electricalmachine to a tractive element of the vehicle; a first clutch selectivelyrotationally coupling the first carrier and the second carrier to thedriveshaft when engaged; at least one of: a second clutch selectivelyrotationally coupling the second electrical machine to the connectingshaft when engaged; and a third clutch selectively rotationally couplingthe second gear set to the driveshaft when engaged; and a brakepositioned to selectively limit a rotation of the first carrier and thesecond carrier, wherein the drive system is selectively reconfigurableinto a mode whereby the brake and the second clutch are engaged.